I have the same setup, modified Hemi with roller, Vavoline VR1 10-30 is great. If I didn't have cold weather - or - I raced more, I would use the 20-50.

Can you talk to the engine builder to ask for their recommendation?

The 12 Scariest Words in the English Language: We are here from the Government and we want to help you. 1968 Plymouth Road Runner, Hemi and much more 1968 Dodge Charger, 318 and not much else 1958 Dodge Pick Up, 383 and loud 1966 Dodge Van, Slant 6 and cool